/*
 * Copyright (c) 2003, KNOPFLERFISH project
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following
 * conditions are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above
 *   copyright notice, this list of conditions and the following
 *   disclaimer in the documentation and/or other materials
 *   provided with the distribution.
 *
 * - Neither the name of the KNOPFLERFISH project nor the names of its
 *   contributors may be used to endorse or promote products derived
 *   from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package org.knopflerfish.bundle.http;

public abstract class ObjectPool
{
  // private fields

  private final PoolableObject[] pooledObjects;

  private int count = 0;

  // constructors

  public ObjectPool()
  {
    this(10);
  }

  public ObjectPool(final int maxInstances)
  {
    this(maxInstances, 0);
  }

  public ObjectPool(final int maxInstances, final int createInstances)
  {
    pooledObjects = new PoolableObject[maxInstances];

    count = 0;
    while (count < createInstances) {
      put(createPoolableObject());
    }
  }

  // protected abstract methods

  protected abstract PoolableObject createPoolableObject();

  // public methods

  public PoolableObject get()
  {
    PoolableObject object;
    synchronized (pooledObjects) {
      if (count == 0) {
        object = createPoolableObject();
      } else {
        object = pooledObjects[--count];
      }
    }
    object.init();

    return object;
  }

  public void put(PoolableObject object)
  {
    object.destroy();
    synchronized (pooledObjects) {
      if (pooledObjects.length > count) {
        pooledObjects[count++] = object;
      }
    }
  }

} // ObjectPool
